System and method for real-time ultrasound guided prostate needle biopsies using a compliant robotic arm

Abstract

Systems and methods are provided for utilizing an MRI image and real-time an ultrasound images to guide and/or restrict the movement of an ultrasound probe in position for collecting a biopsy core. A real-time ultrasound image is acquired and fused with pre-operative imaging modalities, such as an MRI image, to provide a three-dimensional model of the prostate. A multi-link robotic arm is provided with an end-effector and an ultrasound probe mounted thereto. Sensor information is used to track the ultrasound probe position with respect to the 3D model. The robotic arm allows for the implementation of a virtual remote center of motion (VRCM) about the transrectal probe tip, an adjustable compliant mode for the physician triggered movement of probe, a restrictive trajectory of joints of the robotic arm and active locking for stationary imaging of the prostate.

We claim: 
     
       1. A system for ultrasound guided prostate needle biopsies using a robotic arm, the system comprising:
 a processor configured to receive a preoperative three-dimensional image of a prostate, wherein the processor is further configured to generate a three-dimensional model of the prostate based on the received image; 
 a multi-link robotic arm comprising:
 a plurality of joints; 
 an end-effector attached to one of the plurality of joints; 
 an ultrasound probe attached to the end-effector, wherein the ultrasound probe is operably connected to the processor to capture an ultrasound image, wherein the preoperative three-dimensional image was captured using a different imaging modality from the ultrasound image, wherein the processor updates the three-dimensional model of the prostate based on the captured ultrasound image; 
 a position sensor for at least one of the plurality of joints, the position sensor operably connected to the processor to map the position of the ultrasound probe with the updated three-dimensional model; and 
 a force sensor operably connected to the processor, wherein the force sensor is configured to detect input forces to the end-effector, 
 
 wherein the processor, the position sensor and the force sensor comprise a control loop configured to control manipulation of the ultrasound probe based on updates to the three-dimensional model of the prostate, and 
 wherein the robotic arm is configured to operate in a first operating mode restricting movement of the ultrasound probe about a distal end of the ultrasound probe to maintain pressure on the prostate based on consecutively captured ultrasound images in automatic performance of a three-dimensional ultrasound sweep of the prostate. 
 
     
     
       2. The system of  claim 1  wherein the force sensor is attached to a handle of the ultrasound probe. 
     
     
       3. The system of  claim 2  wherein the robotic arm is configured to operate in a plurality of other operating modes to restrict movement of the ultrasound probe, the plurality of other operating modes comprising:
 a second operating mode restricting movement of the ultrasound probe by mechanical limits of the robotic arm; 
 a third operating mode passively guiding movement of the ultrasound probe into a position to collect a biopsy core; 
 a fourth operating mode restricting all movement of the ultrasound probe; and 
 a fifth operating mode restricting movement of the ultrasound probe based on analysis of captured ultrasound images. 
 
     
     
       4. The system of  claim 3  wherein the processor is configured to identify the biopsy core based on the received three-dimensional image of the prostate and the captured ultrasound image of the prostate. 
     
     
       5. The system of  claim 1  wherein the pressure is maintained on the prostate based on de-correlation between the consecutively captured ultrasound images. 
     
     
       6. The system of  claim 1  wherein the pressure is maintained on the prostate based on a difference in a strain on prostate tissue between the consecutively captured ultrasound images. 
     
     
       7. The system of  claim 1  wherein the pressure is maintained on the prostate based on an image confidence map generated based on the consecutively captured ultrasound images. 
     
     
       8. The system of  claim 1  wherein the pressure is maintained on the prostate based de-correlation between the consecutively captured ultrasound images, strain on prostate tissue between the consecutively captured ultrasound images and an image confidence map generated based on the consecutively captured ultrasound images. 
     
     
       9. The system of  claim 1 , wherein the control loop is configured to provide adjustable compliance of the multi-link robotic arm. 
     
     
       10. The system of  claim 1  wherein the control loop is configured to restrict motion of the ultrasound probe. 
     
     
       11. The system of  claim 1  wherein the preoperative three-dimensional model comprises a voxel representation of the prostate with prostate information. 
     
     
       12. The system of  claim 11  wherein the prostate information comprises tissue properties, biomechanical properties, or biomechanical relationships. 
     
     
       13. The system of  claim 1  wherein the processor is configured to identify a size of a biopsy core based on the received three-dimensional image of the prostate and the captured ultrasound image of the prostate.